Typical clutch systems include a clutch input such as a clutch basket, a clutch output such as a center clutch, and one or more plates making up a clutch pack and disposed between the clutch input and clutch output. When the clutch pack is compressed, the clutch input and clutch output become rotationally coupled. The clutch pack is typically compressed by a pressure plate; the pressure plate typically providing a compressive force via a spring mechanism or through a centrifugally actuated mechanism.
Typically, such clutch systems include a clutch disengagement system consisting of a lever mechanically coupled to the pressure plate such that when the lever is actuated, the pressure plate's compressive force on the clutch pack is removed, disconnecting the rotational coupling between the clutch input and clutch output. Clutch disengagement systems typically couple the lever to the pressure plate mechanically through a hydraulic actuation system or a cable actuation system.
Most motorcycles incorporate a manual transmission coupled to the engine via a multi-plate clutch assembly. Typically, the multi-plate clutch is engaged/disengaged by the driver via a lever mounted on the handlebar. Although the lever operated clutch allows the driver to control the clutch engagement/disengagement, often times motorcycle drivers find the clutch lever difficult to operate smoothly. New riders have difficulty adjusting to smoothly engaging the clutch while operating the throttle to move the vehicle from a standing start. Experienced riders may need to partially disengage the clutch when traveling slowly to allow the engine to continue running without stalling. Motorcycle racers often have a difficult time controlling the engagement of the clutch and the application of the throttle to maximize acceleration. Off-road motorcycle racers often need to stop the rear wheel suddenly with the rear brake, causing the engine to stall if the clutch is not first disengaged. An automatic clutch can help overcome many of the problems associated with a manual clutch.
U.S. patent application Ser. No. 12/412,245 discloses an automatic clutch system incorporating an expanding friction disk and is incorporated herein by reference. One of the benefits of the improved automatic clutch system is the ability for the operator to override the automatic engagement of the clutch via a clutch lever without a significant change in how the clutch lever responds due to the centrifugal mechanism in the automatic clutch. Such a clutch system requires the pressure plate to be lifted away from the clutch pack to function properly. In application Ser. No. 12/412,245, lifting the pressure plate away from the clutch pack is accomplished with an adjuster within the engine cases.
However, for some motorcycle operators, the ability to adjust the position of the pressure plate without opening the engine cover to gain access to the clutch is important. Being able to adjust the position of the pressure plate externally allows the operator to make adjustments to the clutch system to compensate for clutch pack wear for example. By adjusting the position of the pressure plate so that it comes in contact with the clutch pack, allows the operator to quickly and easily configure the clutch so that when the engine is not spinning, the clutch is engaged. In this configuration, the clutch operation is similar to a manual clutch and allows the operator to “bump start” the engine. When the engine is off, with a gear selected and the clutch lever disengaged, rolling the motorcycle at sufficient speed and then suddenly releasing the clutch lever to engage the clutch, can start the engine.
Clutch disengagement systems utilizing a cable for the mechanical connection between the lever and the pressure plate are well known in the art and typically incorporate a cable end adjuster to accommodate for wear or expansion of the clutch pack. Such clutch disengagement systems are typified by the system provided on the 2009 Honda CRF450R motorcycle model and whose operation and adjustment are disclosed in the 2009 Honda CRF450R Owner's Manual.
The cable end adjuster allows the operator to increase or decrease the amount of lever “free-play”. Lever “free-play” is defined as the movement of the lever between an outward stopping point of the lever against the lever mounting bracket or perch and inward movement until further movement of the lever will result in lifting of the pressure plate. Typically, the cable adjuster is positioned so that the lever has some “free-play” movement. By adjusting the cable end adjuster for more “free-play”, the operator must move the lever further before the pressure plate begins to lift. With less “free-play”, the operator will not need to move the lever as far before the pressure plate begins to lift. The cable end adjuster can typically be adjusted to remove all “free-play” movement and further adjustment of the cable end adjuster will result in the pressure plate being lifted above the clutch pack. In this state, there is no lever “free-play” but the cable end adjuster has been used to create the necessary gap between the pressure plate and the clutch pack for the expanding friction disk to function as described in application Ser. No. 12/412,245. The disadvantage to this type of configuration is that the clutch lever has no “free-play” and can be more difficult for the operator to pull in to disengage the clutch system.
For typical hydraulic clutch disengagement systems, no such provision exists for lifting the pressure plate through an in-line external adjuster.
Hydraulic clutch disengagement systems are well known in the art and are typified by systems made by Magura and Brembo and are included on motorcycles such as those provided by KTM such as the KTM model year 2010 KTM 250 XCW.
A typical hydraulic clutch disengagement system includes a master cylinder incorporating a reservoir for hydraulic fluid and a lever acting on a piston. A slave cylinder incorporates a bore and a piston; the piston typically acts upon the clutch throwout to lift the pressure plate for disengagement. A hydraulic line typically couples the master and slave cylinders and provides a conduit for the hydraulic fluid.
When the clutch lever is in the disengaged position, typically an open port exists between the slave cylinder piston and the reservoir of the master cylinder. When the clutch lever is in the engaged position, the open port between the reservoir and the slave cylinder is closed and no self-adjustment can take place. The slave cylinder typically incorporates a spring that pushes the piston in the slave cylinder towards the pressure plate. Because an open port exists to the master cylinder reservoir, the slave cylinder is free to move inward or outward towards the pressure plate; when the clutch lever is in the disengaged position.
Therefore a need exists for an adjustment mechanism, external to the engine cases, that can lift the clutch pressure plate to create a gap between the clutch pressure plate and clutch pack.
For a cable actuated clutch disengagement system, the adjustment mechanism should be provided to allow a gap between the clutch pressure plate and clutch pack while maintaining clutch lever free play and use of the clutch lever. For hydraulically actuated clutch disengagement systems, the adjustment mechanism should maintain the use of the clutch lever while providing the capability to lift the clutch pressure plate to create a gap between the clutch pressure plate and clutch pack.
It is therefore an object of the present invention to provide an adjuster mechanism, external to the engine cases, for a cable actuated clutch disengagement system that allows a gap between the pressure plate and clutch pack to be created while maintaining clutch lever “free-play”.
It is another object of the invention to provide an adjuster mechanism, external to the engine cases, for a hydraulically actuated clutch disengagement system that allows a gap between the pressure plate and clutch pack to be created while maintaining the function of the hydraulically actuated clutch disengagement system.
A preferred embodiment of the present invention for cable actuated clutch disengagement systems is disclosed in FIGS. 5 through 8. A preferred embodiment of the present invention for hydraulically actuated clutch disengagement systems is disclosed in FIGS. 9 through 12. FIGS. 1A and 1B depict a typical clutch system positioned relative to the present invention. FIGS. 2 through 4 depict a clutch assembly similar to what is disclosed in U.S. patent application Ser. No. 12/412,245 with the clutch pressure plate positioned in three typical states.